Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$29.52	4.114%	$30.7345	$30.73	$30.75	$30.70
Purchase #2	$152.46	13.337%	$172.7936	$172.79	$172.80	$172.80
Purchase #3	$97.85	3.607%	$101.3794	$101.38	$101.40	$101.40
Purchase #4	$207.92	7.526%	$223.5681	$223.57	$223.55	$223.60
Purchase #5	$195.65	13.844%	$222.7358	$222.74	$222.75	$222.70
Purchase #6	$219.35	4.470%	$229.1549	$229.15	$229.15	$229.20
Purchase #7	$183.49	4.663%	$192.0461	$192.05	$192.05	$192.00
7 purchase totals =	$1,086.24		$1,172.4124	$1,172.41	$1,172.45	$1,172.40